1. Field of The Invention
The present invention relates to a vehicle door lock device provided with an anti-theft mechanism. The anti-theft mechanism is also called a super-lock mechanism or a deadlock mechanism.
2. Description of The Related Art
A previously known vehicle door lock device has a lock lever which is turned between a locked position and an unlocked position by either operating a door key cylinder mounted on the outer surface of the door, or an inside locking button mounted on the inner surface of the door. The conventional lock lever is sometimes displaced to the unlocked position illegally by gripping the locking button by means of a gripping tool inserted between the door and a vehicle body without a door key.
As countermeasures against such an illegal act, many conventional anti-theft mechanisms for canceling the connection between the inside lock button and the lock lever have been proposed.
FIG. 4 is a schematic diagram for illustrating the configuration of a lock device provided with an anti-theft mechanism, which is described in U.S. Pat. No. 4,978,154. This conventional lock device has a lock lever A rotatably supported on a shaft C and adapted to be displaced between a locked position and an unlocked position; an anti-theft member B adapted to be displaced between an anti-theft position and a canceling position by sliding in the left and right direction; a button lever F connected to an inside locking button G and adapted to be turned together with the anti-theft member B; and a switching lever H perforated with an elongated hole I in which a projection D of the member B is engaged. When the anti-theft member B is in the anti-theft position as shown in FIG. 4, the projection D of the member B is disengaged from a forked portion E of the lock lever A. Thus, even if the button lever F and the anti-theft member B are turned clockwise by operating the inside locking button G, the projection D can not cause the lock lever A to turn to the unlocked position. When canceling an anti-theft condition, the anti-theft member B is slid to the right by turning the switching lever clockwise, so that the projection D of the anti-theft member B is engaged with the forked member E. Then, the anti-theft member B is connected with the lock lever A. Consequently, the inside locking button G comes to be able to cause the lock lever A to turn to the unlocked position.
In each case of many anti-theft mechanism conventionally proposed, the anti-theft member will be displaced under power of a motor. There are two methods by which the motor is activated or operated. One of the methods is that a controller operates the motor for displacing the anti-theft member to the anti-theft position when turning the door key cylinder to the locked position. A problem for this method is that the anti-theft member is automatically put in the anti-theft position when the lock lever is changed to the locked position by use of a door key. Namely, in the case of employing this method, it becomes impossible to change only the position of the lock lever without moving the anti-theft member.
The other method is to establish in the door key cylinder a special position for an anti-theft operation. The controller operates the motor for changing the anti-theft member to the anti-theft position only when the key cylinder is turned to the special position or anti-theft position. In the case of employing the latter method, a driver can freely select one of a normal locked condition in which the lock lever and the anti-theft member are in the locked position and the canceling position, respectively, and an anti-theft locked condition in which the lock lever in the locked position and the anti-theft member in the anti-theft position.
The latter method, however, has a problem in that not many malfunctions occur. As shown in FIG. 5, the door key cylinder to be used in performing the latter method has the special position or anti-theft position in addition to three conventional positions which ordinary key cylinders have, namely, a locked position, an unlocked position and a neutral position provided therebetween. This anti-theft position is established beyond the locked position. Thus, if the driver wishes for a normal lock, the key cylinder is turned to the locked position but should not be turned beyond the locked position. However, many malfunctions do occur when turning the key cylinder beyond the locked position.